Abstract 668: DNA methylation of apoptosis-related genes as clinical biomarker in rectal cancer.

Background: To prevent over- and undertreatment of rectal cancer patients, there is a need for the development of new biomarkers that can complement the current staging system. We have previously shown that apoptosis plays an important role in local tumor recurrence after TME surgery. We studied the epigenetic regulation of several key apoptosis genes in rectal cancer tissues, using methylation-sensitive restriction enzymes. Materials and methods: DNA was obtained from frozen specimens of 138 patients representative for the non-irradiated arm of the Dutch Total Mesorectal Excision (TME) trial. Isoschizomers HpaII (CpG methylation sensitive) and MspI (not sensitive) were used for restriction enzyme digestion of tumor DNA, followed by real-time PCR for apoptosis genes Apaf1, Bcl2, TrailR2, Fas and p53. A pilot series consisted of 50 patients with tumor stages I-III and 10 normal rectal tissues. For the validation study stage III patients (n=88) and 18 normal rectal tissues were selected. Results: Single marker analyses showed a significant correlation between methylation status and apoptotic status (measured by immunohistochemical staining of M30) of Fas (p=0.005) and Apaf1 (p=0.052). Combining intrinsic pathway markers Apaf1, Bcl2 and p53, significant differences were observed between the methylation groups in survival and recurrence analyses (log rank test), with overall survival (p=0.054), cancer specific survival (p=0.014) and distant recurrence free survival (p=0.006). Conclusion: Methylation of apoptosis genes is representative for the apoptotic status of a tumor and is correlated to survival and recurrence in rectal cancer patients. The apoptotic status of a tumor may be used to guide treatment strategies for individual patients. [A.B. and E.C.M.Z contributed equally to this work.] Citation Format: Anne Benard, Eliane C.M. Zeestraten, Ines J. Goossens-Beumer, Hein Putter, Christine Kuo, Cornelis J.H. van de Velde, Peter J.K. Kuppen, Dave S.B. Hoon. DNA methylation of apoptosis-related genes as clinical biomarker in rectal cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 668. doi:10.1158/1538-7445.AM2013-668